Remotely controlled brachytherapy unit

ABSTRACT

A method and apparatus is provided whereby a point or elongate radioactive source is introduced into the body of a patient and a source is subsequently oscillated whereby the spacial distribution of radioactivity can be varied to give spherical, oblate spheroidal or cigar-shaped configuration. The invention further contemplates arcuate oscillation in addition to linear oscillation.

United States Patent 1191 Whitfield Feb. 11, 1975 I REMOTELY CONTROLLED[56] References Cited BRACHYTHERAPY UNIT UNITED STATES PATENTS [75] In etor: ouglas Whitfield, S e, 3,426,196 2/1969 OShea et al. 250/308Ontario, Canada 3,669,093 6/1972 Sauerwein et a]. 250/496 [73] Assignee:Atomic Energy of Canada Limited, I

Ottawa, Ontario Canada Primary Examiner-Archie R. Borchelt Attorney,Agent, or FirmCushman, Darby & [22} Filed: Nov. 9, 1973 Cushman [2!]Appl. No.: 414,436

Related US. Application Data [57] ABSTRACT [63} Continuation of Ser. N0.266,507, June 26, 1972, 1 A method and apparatus is provided whereby apoint abandoned. or elongate radioactive source is introduced into thebody of a patient and a source is subsequently oscil- [30] ForeignApplication Priority Data Iated whereby the spacial distribution ofradioactivity May 15, 1972 Canada 142103 can be varied to giveSpherical, oblate spheroidal or cigar-shaped configuration. Theinvention further con- 52 11.5. C1. 250/497, 250/496 templates arcuateOscillation in addition t9 linear 51 1111. C1. c2111 5/00, G2lk 1/009111mm- Fleld of Search C i 8 Drawing gu es REMOTELY CONTROLLEDBRACHYTI-IERAPY UNIT This is a continuation, of application Ser. No.266,507 filed June 26, 1972, now abandoned.

This invention is related to a method and apparatus for accuratelylocating a source of radioactive emmission in relation to and operableupon a volume of material to be irradiated and to the subsequentoscillation of the source whereby the distribution of the irradiation isnon-spherical. The invention has particular, but not exclusive,application in brachytherapy. The word brachytherapy is derived frombrachys (Gk) meaning short and therepauein (Gklmeaning take care of.Thus, in the present context, the word brachytherapy means treatment inclose. The present invention,

however, envisages brachytherapy by remote control in order to protecthospital personnel against radiation hazards.

For years doctors have had to place, by hand, small radioactive sourcesinside the patient often through the natural openings of the body. Thistype of procedure has many drawbacks. It is not always positive orprecise. It is extremely dangerous to the medical staff, uncomfortablefor the patient and it entails extremely long treatment time. Because ofthese factors, it was not possible to employ powerful radiation sourcessuch as Cobalt 60. The present invention overcomes the above factors byproviding a method and an apparatus which places the source in close tothe tissue, for example, a tumour, by remote control with precision andsafety. The present invention further provides for considerablevariation in the shape of the distribution or isodose curves. A singlehomogeneous source pellet of substantially spherical shape has, ofcourse, spherical distribution if stationary. The same source, ifoscillated along a straight line, will provide oblate spheroidaldistribution. If a string of similar pellets in juxtaposition isoscillated, along a straight line, the distribution will'becigar-shaped, that is, substantiallly cylindrical with hemisphericalends. The use ofa string of source pellets has a distinct advantage inthat it is not essential that the individual source-strengths of thepellets be equal. (Equality of source strength is difficult andimpractical to obtain). The effect of variations between the individualsources is nullified when the string is oscillated and the netdistribution can be quickly established by a calibration technique.

The invention will now be described with reference to the accompanydrawings, in which:

FIG. 1 is a side view of aunit assembly comprising a control unit andsource container.

FIG. 2 shows a catheter, in part section, and a catheter coupling.

FIG. 3 shows a brachtherapy control panel.

FIG. 4 shows a screw mechanism for effecting movement and oscillation ofthe catheter drive cable.

FIGS. 5 and 6 are right and left hand views of the screw mechanism.

FIG. 7 shows a source position control.

FIG. 8 shows a source container lock switch assembly, (disconnectcoupling).

Referring to FIG. 1, there is shown a control unit assembly l, a sourcecontainer stand assembly 8, flexible hose and disconnect couplingassemblies 13 which extend between the control unit assembly 1 and thesource container stand assembly 8. Additional cable 2 guide hoseassembly flexible tubes extend from the source container stand assembly8 to catheter coupling assemblies 10 and hence to the catheterassemblies 11.

Referring to FIG. 2, there is shown a catheter coupling 10 whichterminates flexible hose 14 and which receives-catheter assembly 11. Thecatheter I10 is shown partly in section to disclose a source capsule112, in the fully out position and movable by means of the drive cableattached thereto. Electrical cables 144, 146 are used in conjunctionwith contacts, not shown, within the coupling 10 which contacts areconnected to and operable upon a Catheter Secured warning light 607 onFIG. 3.

The drive cable 140, which slides within the flexible hose 14 passesthrough the source container assembly 8, through a disconnect couplingassembly at 800 and through the hose assembly 13 wherein the cable.enters the control unit assembly 1. The drive cable is of the type thathas a flexible core around which is formed a spaced apart helicalwinding for co-operation with a drive member. Such a drive cable isknown in the trade under the trademark Teleflex. The drive cable, afterentering the control unit assembly, passes through a cable driveassembly 200 where it turns through about 90 to continue upwardly to andaround a pulley 210 and downwards to be terminated with a counter weight220. As shown in FIG. 1, the weight 220 is at its lowest positioncorresponding to withdrawal of the source capsule 112 into the sourcecontainer stand assembly 8. The weight 220 slides within a tube 230 andboth the weight and the tube are of non-circular cross-section, forexample square, to prevent rotation of the weight with consequentialslight variation in the effective length thereof. Referring again toFIG. 1, that portion of the drive tube vertically disposed above thecable drive assembly 200 passes through a source position controlassembly which will now be discussed in detail with reference to FIG. 7.The tube is longitudinally slotted as at 240 between a top plate 242 andbottom plate 244. The plates 242 and 244 support vertical bearing shafts246 upon which slide saddles 248, 250. The slide saddlesv 248, 250 carrymicro-switches 260, 262 and 258, respectively, having actuator wheels266, 26 and 264. The actuator wheels are selectively depressed by amicro-switch actuator 270 which is also indicated in FIG. 1. The topsaddle 248 can be lowered until mechanically prevented by a stop 272which may also be used for setting an indicator on the control panel tozero in a manner to be described.

The actual setting of the top and bottom saddles is effected by means oflimit switch control cables, one of which is shown at 281 in FIG. 1. Thecables extend between the saddles and control knobs to be described.Referring to FIG. 3 there is shown a control console 300 which ismounted on the front of the control unit assembly 1 in FIG. 1. Theconsole shown is intended for controlling the movement and oscillatin ofthree catheters. The controls on the right hand side will be described.Knobs 310, 320 control individual control box assemblies, 312 on FIG. 1.Rotation of the knob 310 moves the lower saddle 250 up or down by cable281. Similarly, rotation of the knob 320 moves the upper saddle 248.Each of the limit switch control cables 281, 283 are extended upwardsfrom the control box assemblies 312 to move upper and lower positionindicators 330, 340, which co-operate with a scale 350. The 0" mark, atthe bottom of the scale, corresponds to the source capsule 112 beingfully extended into the catheter 110 as shown in FIG. 2, and occurs whenthe microswitch actuator 270 depresses the lower micro-switch 258 inFIG. 5. The scale is marked up to 16 cms. If the upper indicator 330 isopposite the 16 mark, upper micro-switch 260, in FIG. 5, will bedepressed by actuator 270. As stated previously, the drive cable 130 ismoved by a cable drive assembly 200 which is driven by motor 400 inFIG. 1. The cable drive assembly 200 is fitted with sprocket 402 havingroller chain 404 thereon which, in turn, drives sprocket 406 on a screwmechanism now to be described with reference to FIGS. 4, 5, and 6. Thetorque from the motor 400 is transmitted through electromagneticclutches, now shown.

The screw mechanism assembly, generally indicated at 500, comprises abase 502, bearings 504, 506 which support an actuating screw 508.

A nut 512, having an internal thread of size and pitch to cooperate withthe screw 508, is longitudinally movable in response to rotation of thescrew 508. In order to prevent the nut 512 from rotating, a circular rod514 extends from end-to-end of the screw 508 and is restricted againstlongitudinal movement by a set screw 516 in bearing 504.

Adjacent to the left-hand end of the screw 508 is an upstanding rib 516to which micro-switches 522, 524 and 526 having actuating plungers 528,532, and 534 respectively. Longitudinal adjustment, and clamping of themicro-switches is effective by a set-screw 536 and micrometer screw 537.

Adjacent to the right-hand end of the screw 508 is an upstanding flange542 to which are fastened microswitches 544, 546 having actuators 548,522 respectively. These switches are adjustably mounted and positionedby micrometer screw 555 and clamped by screw 554.

The nut 512 carries upper and lower micro-switch depressors 562, 564which are vertically aligned to cooperate with micro-switches 524 and546' or 526 and 544 respectively. The nut 512 also includes an extension560 which operates solely upon micro-switch 522.

The number of teeth on sprockets 402 and 406, which are interconnectedby chain 404 are selected so that, together with the pitch of the screw508, the nut 512 moves the entire operational length of the screw whilethe source capsule moves from its fully extended position, as shown inFIG. 2, to its stored position within the source container stand 8. Inthe present embodiment there is an 8:1 reduction of the linear movementbetween the cable and the screw. The motor 400 in FIG. 1 which effectsmovement of both the catheter and the screw 508 is connected so thatlimit switch 524 disconnects the power supply to the motor when the nut512 is near the left hand extremity of its movement. Similarly,microswitch 544, effects disconnection of the motor near the right handextremity of the movement of the nut.

Operation of the micro-switches will now be described in greater detail.

The right hand end screw corresponds to the SOURCE SAFE or withdrawncondition of the source capsule from the catheter. At the SOURCE SAFEend of the screw mechanism, micro-switch 546 controls a SOURCE SAFEindicator lamp 600 in FIG. 3. Microswitch 544 controls a SOURCEOVERTRAVEL indicator lamp 602 in FIG. 3. At the SOURCE EXPOSED end ofthe screw mechanism, micro-switch 526 controls the SOURCE OVERTRAVELindicator lamp 603. At the same end, micro-switch 522 locks in aslowspeed reduction when the source is to be oscillated. Mi-

5 cro-switch 522 is also used in connection with a dummy source for setup purposes.

Once a source has been transferred from the storage position, the lamp600 is extinguished and lamp 606 is turned on (by micro-switch 526). Thesource may then be maintained stationary or oscillated by suitablysetting switch 604. I

Referring now to FIG. 8 there is shown a source con tainer lock switchand a cable disconnect assembly generally indicated at 800. The assemblyis fastened to the source container stand 8, shown in FIG. 1, a portionof which stand is indicated at 81. A portion of the drive cable 130between the control unit and source container and the catheter end ofthe drive cable 140 between the control unit assembly 1 are shown. Asource lock 802 is provided to prevent unauthorized or accidentalwithdrawal of the source from the container 8. When the body of the lockis withdrawn, by operation of a key, not shown a micro-switch 804 isdepressed and the switch is connected to and operable upon a warninglight 608 on FIG. 3. In order to disconnect the drive cable 130 from thesource cable 140, asleeve 806 is provided. The sleeve is fastened to thebody of the switch by means of set screws 810. When the set screws arewithdrawn, the sleeve 806 may be withdrawn to the left in the drawing toexpose a split collar 808. Removal of the two halves of the split collar808 enables withdrawal of a roll pin 812 which joins the drive cable 130to the source cable 140.

In operation, the catheter 11 is placed in the desired irradiatinglocation before the source is advanced into the catheter. This isaccomplished without hazard to the medical staff as the source is safewithin the source container. The catheter 11 is then coupled to thecatheter coupling whereupon indicator lamp 607 on the control console isactivated.

The source may consist of a single pellet of radioactive material, forexample, Cobalt 60, or it may comprise a number of pellets arranged inline formation.

The single pellet may be used in a fixed position or oscillated alongthe axis of the catheter. The line of pellets may be oscillated in asimilar manner. A single stationary pellet gives a substantiallyspherical distribution where a single pellet, when oscillated, givesoblate spheroidal distribution. A line of juxtaposed pellets, whenoscillated, gives s substantially cigar-shaped distribution.

While the catheter shown is straight, bent catheters have been used withequal success.

I claim:

1. A method of selectively distributing the radioactive emission from asource disposed to irradiate a given volume of material in apredetermined pattern in the body of a patient, comprising the steps of:

disposing a source in a selected position in the body of a patient,

oscillating said source about said selected position for a selectedperiod of time, and

enclosing the source ina container which is fixed relative to said bodyof said patient wherein the distribution of radioactive emission isnon-spherical.

2. The method of claim 1 further including the step of automaticallywithdrawing said source away from said body of said patient to anon-radiation positin immediately following cessation of theoscillation.

3. The method of claim 1 further including the step of utilizing theforce of gravity to automatically withdraw said source away from saidbody to a nonirradiation position immediately following cessation of theoscillation.

4. The method of claim 1 wherein said distribution of emission issubstantially oblate spheroidal.

5. The method of claim 1 wherein said distribution of emission issubstantially cigar-shaped.

6. The method of claim 1 wherein said source comprises a single pellet.

7. The method of claim 1 wherein said source comprises a plurality ofpellets of substantially equal source-strength.

8. The method of claim 1 wherein said source comprises a plurality ofpellets of diffusing sourcestrengths.

9. A method of selectively distributing the radioactive emission from asource disposed to irradiate a given volume of material, comprising thesteps of:

disposing a source in a selected position relative to a volume,oscillating said source about said selected position for a selectedperiod of time, and enclosing the source in a container which is fixedrelative to said volume wherein the distribution of radioactive emissionis non-spherical.

10. A method as in claim 9, including the additional step ofautomatically withdrawing said source away from said volume to anon-irradiation position immediately following cessation of theoscillation.

11. A method as in claim 9, including the additional step of utilizingthe force of gravity to automatically withdraw said source away fromsaid volume to a nonirradiation position immediately following cessationof the oscillation. position immediately following cessation of theoscillation.

12. A method as in claim 9, wherein said distribution of emission issubstantially oblate spheroidal.

13. A method as in claim 9, wherein said distribution of emission issubstantially cigar-shaped.

14. A method as in claim 9, wherein said source comprises a singlepellet.

15. A method as in claim 9, wherein said source comprises a plurality ofpellets of substantially equal source-strength.

16. A method as in claim 9, wherein said source comprises a plurality ofpellets of diffusing sourcestrengths.

1. A method of selectively distributing the radioactive emission from asource disposed to irradiate a given volume of material in apredetermined pattern in the body of a patient, comprising the steps of:disposing a source in a selected position in the body of a patient,oscillating said source about said selected position for a selectedperiod of time, and enclosing the source ina container which is fixedrelative to said body of said patient wherein the distribution ofradioactive emission is non-spherical.
 2. The method of claim 1 furtherincluding the step of automatically withdrawing said source away fromsaid body of said patient to a non-radiation positin immediatelyfollowing cessation of the oscillation.
 3. The method of claim 1 furtherincluding the step of utilizing the force of gravity to automaticallywithdraw said source away from said body to a non-irradiation positionimmediately following cessation of the oscillation.
 4. The method ofclaim 1 wherein said distribution of emission is substantially oblatespheroidal.
 5. The method of claim 1 wherein said distribution ofemission is substantially cigar-shaped.
 6. The method of claim 1 whereinsaid source comprises a single pellet.
 7. The method of claim 1 whereinsaid source comprises a plurality of pellets of substantially equalsource-strength.
 8. The method of claim 1 wherein said source comprisesa plurality of pellets of diffusing source-strengths.
 9. A method ofselectively distributing the radioactive emission from a source disposedto irradiate a given volume of material, comprising the steps of:disposing a source in a selected position relative to a volume,oscillating said source about said selected position for a selectedperiod of time, and enclosing the source in a container which is fixedrelative to said volume wherein the distribution of radioactive emissionis non-spherical.
 10. A method as in claim 9, including the additionalstep of automatically withdrawing said source away from said volume to anon-irradiatiOn position immediately following cessation of theoscillation.
 11. A method as in claim 9, including the additional stepof utilizing the force of gravity to automatically withdraw said sourceaway from said volume to a non-irradiation position immediatelyfollowing cessation of the oscillation. position immediately followingcessation of the oscillation.
 12. A method as in claim 9, wherein saiddistribution of emission is substantially oblate spheroidal.
 13. Amethod as in claim 9, wherein said distribution of emission issubstantially cigar-shaped.
 14. A method as in claim 9, wherein saidsource comprises a single pellet.
 15. A method as in claim 9, whereinsaid source comprises a plurality of pellets of substantially equalsource-strength.
 16. A method as in claim 9, wherein said sourcecomprises a plurality of pellets of diffusing source-strengths.